The present invention relates to portable machine tools, and more particularly to such machine tools in which a first tool element is reciprocated relative to a second tool element to perform machine operations in a single stroke or cycle.
Portable machine tools employing electric or hydraulic motors to perform various machining operations upon a workpiece have gained substantial acceptance and are now widely employed. Some of these machines are designed to effect a continuous series of repetitive strokes or cycles of the tool elements relative to each other over a substantial length of the workpiece, as, for example, shears to effect the cutting of the metal, or a punch and die mechanism to perform a nibbling operation. Thus, the tool elements will be relatively reciprocated continuously along the surface of the workpiece for so long as the operator has the operating elements in driving engagement by operation of a manual switch.
However, in some machine tool operations, only a single stroke is desired, such as, for example, in the punching of spaced holes in a workpiece. In such a case, it is desired that the machine tool produce a down stroke to perform the desired work upon the workpiece, and then return in an up stroke to its initial position where it will be stable until the next actuation of the mechanism by the operator. Attempting to produce a single stroke with a machine tool in which the drive motor is normally drivingly engaged with the tool driving mechanism to produce repeat cycles is impractical because of the high speed of the drive motor and the difficulty of stopping the tool elements after a single cycle, particularly in a predetermined position.
Although single cycle machine tools are available, they tend to produce extremely high torque at various points within the drive mechanisms, and the repeated starting and stopping operations will therefore produce substantial wear and tear upon the parts. Moreover, some such tools do not include means for ensuring that the mechanism will be stopped in the most disengaged position of the reciprocating tool element.
It is an object of the present invention to provide a novel portable machine tool having a tool element reciprocatable relative to a fixed tool element in a single complete stroke or cycle, which is highly effective and durable, and which stops the tool element in an initial predetermined position after each complete stroke.
It is also an object to provide such a machine tool in which the elements may be fabricated readily and relatively economically.
A specific object is to provide such a machine tool in which there is provided between first and second gearing levels, a transmission which will be subject to relatively lesser wear and which is coupled to a stop mechanism so as to ensure that the movable machine tool element will be stopped in its upper or remote position.